Lighting systems including light-emitting diodes (LEDs) are becoming increasingly popular for general and targeted lighting in homes, businesses, outdoor areas, and other settings. In comparison to fluorescent lighting systems, LED lighting systems are typically more compact, convenient, and aesthetically pleasing. In comparison to incandescent lighting systems, LED lighting systems are typically more energy efficient. There is also increasing demand for lighting systems with automatic controls that can further improve convenience and energy efficiency. For example, some lighting systems include occupancy sensors that automatically turn lights on only when building occupants are present and automatically turn lights off to save energy when building occupants are not present. As another example, many electricity providers have demand-response programs in which participating electricity customers can receive credits for reducing their electricity consumption during periods of peak overall electricity demand within the provider's power grid.
FIG. 1 is a partially schematic circuit diagram illustrating a conventional lighting system 100 configured for automatic control. The system 100 includes a power source 102, a plurality of fluorescent lighting fixtures 104 (individually identified as 104a-e), and wiring 106 operably connecting the fixtures 104a-e and the power source 102. The fixtures 104a-e individually include leads 108, and the system 100 further includes electrical connectors 110 connecting the leads 108 and the wiring 106 such that the fixtures 104a-e are electrically coupled in series. Two of the leads 108 of the last fixture 104e in the series are connected to one another and electrically insulated within a cap 112. The system 100 further includes an automatic controller 114 operably connected to the wiring 106. The automatic controller 114 is configured to receive a signal 116 from a signal source 118 and to automatically shut off the fixtures 104 in response to the signal 116.
Use of the automatic controller 114 with the lighting system 100 can be problematic. For example, the automatic controller 114 may cause the fixtures 104a-e to shut off at inconvenient times. Demand-response events typically occur when grid-wide electricity demand is highest, which is typically also when individual electricity customers have the greatest need for lighting. Furthermore, completely shutting off the fixtures 104 can adversely affect safety, worker efficiency, merchandising, and/or have other undesirable consequences. Accordingly, while many building owners are eager to implement automatic control for non-lighting systems (e.g., air-conditioning systems and refrigeration systems, among others), the same building owners are often justifiably reluctant to implement automatic control for lighting systems. These building owners may determine that their lighting systems are too important to be automatically controlled even if doing so would reduce costs and/or benefit the environment. By some estimates, lighting may account for as much as 5-10% of all energy use in the United States. Accordingly, improved controls are needed.
One conventional approach to facilitating more widespread adoption of automatic control for lighting systems includes using controllers that dim rather than shut off the light output. Using this approach, lighting systems can provide at least some light during periods of automatically lowered power consumption, e.g., during demand-response events. Unfortunately, many lighting fixtures are not dimmable or require complex retrofitting to become dimmable. Furthermore, lighting fixtures that are dimmable tend to be more expensive, less reliable, and less durable than lighting fixtures that are not dimmable. For example, even many high-end dimmable LED fixtures periodically flicker, unexpectedly shut off, or experience other types of poor or failed operation. For these and/or other reasons, conventional dimming alone may be inadequate to encourage more widespread adoption of automatic control for lighting systems. There is a need for further innovation to address this problem and/or one or more other problems associated with conventional lighting technology.